This sword papercraft is the Scarlet Ribbitar, based on the game MS Paint Adventures. The designer is Kimixmeow. Dave tries to alchemize the Scarlet Ribbitar by combining the Caledscratch with Ruby Contraband. He cannot create it it due to its extremely high cost, which includes 2,000,000 of a type of grist he has not yet encountered. The name is a play on "scimitar", a sword with a curved blade.
Alpha Dave is later seen wielding this weapon against Bec Noir. Dave is seen wielding the sword against Jack at a later point in the three days he's so far spent in the last day before The Scratch, presumably having advanced enough to afford it.
You can download this paper craft model from here: MS Paint Adventures - Scarlet Ribbitar Free Papercraft Download